Different formulations?

Different formulations of the teachings support people facing different conditions and circumstances; this can be appreciated and valued.

You should not always assume that your school is
the best to enrol other people in, that's just another form of
Dharma-bashing: “my school is best, no matter
your conditions.”

To be able to send people to another school, better suited for their circumstances, embodies wiser care than to always
assume your school is appropriate. But to send others to the appropriate
school, you need to know enough about the schools available!

Hopefully, the analysis on
interpreting the teachings might have convinced some Theravādins that
their tradition strongly supports a mindful and healthy curiosity, including
towards the reformulations (which might initially appear as
“surprisingly loose”) by Mahāyāna and Vajrayāna
traditions…
Hopefully, it might also have convinced some followers of the later schools
that Theravāda is not to be overlooked as ‘simple’, and that
Theravāda did directly address ambiguities and subtleties! It's easy
—but delusional— to imagine Mahāyāna as
‘superior’ due to the piling up of hyperbolic elaborations and
interpretations; in fact, Theravāda issued the calls for subtle
enquiries, for precepts not to be taken literally, for a nuanced understanding
of dependency on a context, for an attention to potential exceptions (without
falling in their pointless pre-conception —mental proliferations!
—nor their pre-listing in the rules). Zen students may remember that the first Indian patriarchs of Zen were… Mahākāśyapa and
Ānanda!

Different religions?

There's no valid claim of superiority between the Buddhist schools, only
delusions!

There's no valid claim of ‘fundamental’ separateness between
the Buddhist schools: either delusions, or simply different manifestations of
the same core made suitable for different circumstances!

Rejecting forms of Buddhism as “other religions”
is just a disguised attempt to ‘own’ the “Buddhism”
label (because, of course, once the schools are separated, yours will
be ‘Buddhism’ while others’ will be
e.g. ‘Śākyamunism’ or
‘Nāgārjunism’)…“This is mine” is a prime recipe for
“self view” though, i.e. for perpetual suffering!

There's no valid claim of ‘fundamental’ separateness between
the Buddhist schools, the nuances in “expedient means” are
variations on the same Liberating theme!